Hi!
I'd need help in getting some organic chem worksheets and questions. I want to focus more on polymerization,etc. Besides the drawing part, I'd also hope to have those questions that require me to explain. Did all my organic chem questions in TYS and one Longman assessment book. Don't find them effective because they are pretty basic... and there are some questions that I'm struggling with while my friends are doing them with such ease. So yea, I guess I needa brush up on that.
If you do have the questions, you can choose to post them up for me or PM me. Thanks!
The O's organic chem syallabus is rather basic so theres not really much to test or maybe u can first list out what do u all actually learn in organic chem 1st and we'll see what we can ask u.
Originally posted by dkcx:The O's organic chem syallabus is rather basic so theres not really much to test or maybe u can first list out what do u all actually learn in organic chem 1st and we'll see what we can ask u.
I find that the school's questions are tougher than those you get in TYS. The questions do not ask you to draw any complicated stuff but for school papers, the organic chem questions are those challenging and interesting type... Well, at least still within the range of the O's syllabus, just the the TYS 2008 edition doesnt have them. And do you know how to name an isomer from its structure? For example, methyl propane... just by looking at its structure, how do i know it's methylpropane?
Originally posted by anpanman:
I find that the school's questions are tougher than those you get in TYS. The questions do not ask you to draw any complicated stuff but for school papers, the organic chem questions are those challenging and interesting type... Well, at least still within the range of the O's syllabus, just the the TYS 2008 edition doesnt have them. And do you know how to name an isomer from its structure? For example, methyl propane... just by looking at its structure, how do i know it's methylpropane?
Always try to find the longest chain of carbon and then u start to name the branches.
Eg if u have a question then u can end up with say ethylpropane, its more likely to be 3-methylbutane instead.
It takes practice to learn how to identify the longest chain especially if u are given long chains and not straight forward linear chains but it can be fun.
Originally posted by dkcx:Always try to find the longest chain of carbon and then u start to name the branches.
Eg if u have a question then u can end up with say ethylpropane, its more likely to be 3-methylbutane instead.
It takes practice to learn how to identify the longest chain especially if u are given long chains and not straight forward linear chains but it can be fun.
Sorry, but I still don't get the idea. LOL. ;pppppppppp
If u interested, try naming these.
a) C - C - C - C - C
|
C - C - C
b) C - C - C -C
|
C - C
|
C - C
c) C - C - C -C - C
| |
C C - C
|
C
Originally posted by anpanman:
Sorry, but I still don't get the idea. LOL. ;pppppppppp
If the above is too hard, try these 1st which are much easier. I'll explain these and the above later tonight when i back if u can't figure them out and noone else explains to u.
a) C - C - C - C - C
|
C
b) C - C - C - C
| |
C C
c) C - C - C
| | |
C C C
At the very least if u cannot name them, i wan u at least try to tell me what is the longest chain of carbon whether its a meth, eth, pro, but, pent or hex. Since i am not sure how far your syllabus covers but i believe basic naming of the alkane main chain u should be able to do.
Originally posted by dkcx:If u interested, try naming these.
a) C - C - C - C - C
|
C - C - C
b) C - C - C -C
|
C - C
|
C - C
c) C - C - C -C - C
| |
C C - C
|
C
a) pentylbutane
b)butyl butane? LOL
c)Not sure.
Hey, by the way, after you name the longest C chain, what about the rest of the carbon that are linked separately?
Ok, the easier part
a)pentyl methane
b)butyl ethane
c)Propyl propane?
Almost totally unsure. But that are my guesses for now.
Originally posted by anpanman:
a) pentylbutaneb)butyl butane? LOL
c)Not sure.
Hey, by the way, after you name the longest C chain, what about the rest of the carbon that are linked separately?
Ok, the easier part
a)pentyl methane
b)butyl ethane
c)Propyl propane?
Almost totally unsure. But that are my guesses for now.
None are correct but 2nd set a) is close. Go think about it. I will try to explain further tonight when i back home depending on ur progress.
Just some corrections and let u think further. Your main chain must always be the longest. Since Pent is 5C is longer than But, ur main chain will always be pentane and not butane.
Your understanding of methyl, ethyl etc is wrong. Try to look at the below examples. The longest chain is in red and for this i made them straight and not twist and turn like in the above 6 questions.
Methyl means 1 C chain
Ethyl means 2 C chain
C - C - C - C - C - C - C
|
C (methyl)
C - C - C - C - C - C - C
|
C - C (ethyl)
Originally posted by dkcx:If the above is too hard, try these 1st which are much easier. I'll explain these and the above later tonight when i back if u can't figure them out and noone else explains to u.
a) C - C - C - C - C
|
C
b) C - C - C - C
| |
C C
c) C - C - C
| | |
C C C
Ok, try again...
methyl propane
ethyl butane
propyl propane
Will try the difficult questions later. Gotta study for my prac exam next week. Thanks a lot!
Originally posted by anpanman:
Ok, try again...methyl propane
ethyl butane
propyl propane
Will try the difficult questions later. Gotta study for my prac exam next week. Thanks a lot!
a) longest chain is 5 C so its pentane not propane. Don't be careless.
b and c. Please look at my explain and see what is a ethyl, propyl follows same logic and try again. The tougher questions might not be in ur syllabus cos it will involve adding bi, tri, tetra into the name but i will go through it if u are interested to learn.
Gtg now, cya later and hopefully u have understood something more.
Originally posted by dkcx:a) longest chain is 5 C so its pentane not propane. Don't be careless.
b and c. Please look at my explain and see what is a ethyl, propyl follows same logic and try again. The tougher questions might not be in ur syllabus cos it will involve adding bi, tri, tetra into the name but i will go through it if u are interested to learn.
Gtg now, cya later and hopefully u have understood something more.
Hi.
Still don't understand where i went wrong. thought there are 2 carbon chains for (b) so isn't it ethyl? ok, how exactly does 1 C chain look like? From what i see in the diagram drawn, as long as i see 2 C atoms sticking out of the longest branch, it's considered 2 C chains. Not sure if i perceived it correctly.thanks
If you're eager for a challenging OC question that can be done at 'O' levels, here ya go. But for the record, don't waste your time attempting challenging questions unless you're already able to do ALL the questions in the 'O' level TYS. Prioritize wisely.
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The monoprotic (monobasic) hydroxycarboxylic acid Z, derived from an alarm pheromone used by the African ant, has the molecular formula CH3RC(OH)COOH (where R refers to an alkyl group).
It is known that Z contains 2 chiral carbons (where a “chiral carbon” refers to a carbon atom bonded to 4 different groups).
A solution formed by dissolving 1.0g of Z in 250cm3 of water, had a pH of 2.73; a 25.0cm3 aliquot of this solution required 6.85cm3 of 0.10 mol/dm3 NaOH for neutralization.
Draw the structure of compound Z.
---------------------------------------------
You can look up my Collection of 'O & 'A' Levels Qns Thread pg 6 to check your answer after you've drawn compound Z. If you (ie. any current 'O' level students who wish to attempt this question) wish to discuss a step-by-step approach for this question, I'll leave it to others (eg. current 'A' level students) to guide you through.
Originally posted by anpanman:Still don't understand where i went wrong. thought there are 2 carbon chains for (b) so isn't it ethyl? ok, how exactly does 1 C chain look like? From what i see in the diagram drawn, as long as i see 2 C atoms sticking out of the longest branch, it's considered 2 C chains. Not sure if i perceived it correctly.thanks
Now u need to understand that the longest chain or main chain does not always mean it must be a straight chain.
C - C - C - C
|
C - C
This is a hexane not a ethylbutane. The 6C are still consider the same chain if u redraw and align them together. The line looks longer due to font constrain.
C - C - C - C - C C - C - C - C - C
| |
C - C C - C
Now base on the above explaination, this is a methylhexane since the hexane is the longest chain (red) and not a ethylpentane (blue).
Do u understand this now? If you don't, don't read further and just tell me you don't understand and i'll try explain.
If u can understand this, we'll go on to the last bit of your naming to make a) correct since methylpentane is still not fully correct.
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C - C - C - C - C C - C - C - C - C
| |
C C
Now both the above are methylpentane but are they the same compound?
Since the 2 structures are drawn differently, they are chemically different so how do people differentiate them so we know which is being referred to? We do this by numbering the location of the side chains which is methyl in this case.
1C - 2C - 3C - 4C - 5C
|
C (methyl)
Now this methyl is on carbon 3 so we will call it 3-methylpentane. (Take note that its always a number - compound name, NOT 3,methylpentane, 3.methylpentane etc)
In the above example, whether we count from the left or right, it would be 3 but how about this case?
1C - 2C - 3C - 4C - 5C OR 5C - 4C - 3C - 2C - 1C
| |
C (methyl) C (methyl)
Should the answer be 4-methylpentane or 2-methylpentane?
In organic chemistry, we will always name it with the smaller number choice so the answer will be 2-methylpentane.
Do note that the below 2 are exactly the same
5C - 4C - 3C - 2C - C (methyl) 5C - 4C - 3C - 2C - 1C
| |
1C C (methyl)
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If you have understand everything up to here, please try to now give the correct answer for b) and c) with the proper naming style.
er. if i not wrong.
syallbus only until 4 nia. the carbon required in syallbus. 5072?
ok maybe what i saying is beside the point. sorry.
Originally posted by UltimaOnline:If you're eager for a challenging OC question that can be done at 'O' levels, here ya go. But for the record, don't waste your time attempting challenging questions unless you're already able to do ALL the questions in the 'O' level TYS. Prioritize wisely.
---------------------------------------------
The monoprotic (monobasic) hydroxycarboxylic acid Z, derived from an alarm pheromone used by the African ant, has the molecular formula CH3RC(OH)COOH (where R refers to an alkyl group).
It is known that Z contains 2 chiral carbons (where a “chiral carbon” refers to a carbon atom bonded to 4 different groups).
A solution formed by dissolving 1.0g of Z in 250cm3 of water, had a pH of 2.73; a 25.0cm3 aliquot of this solution required 6.85cm3 of 0.10 mol/dm3 NaOH for neutralization.
Draw the structure of compound Z.
---------------------------------------------
You can look up my Collection of 'O & 'A' Levels Qns Thread pg 6 to check your answer after you've drawn compound Z. If you (ie. any current 'O' level students who wish to attempt this question) wish to discuss a step-by-step approach for this question, I'll leave it to others (eg. current 'A' level students) to guide you through.
This seems abit tough for them. If they can't even name and understand the compounds, i don't think they can draw it out easily.
Not sure how important nomencluture is for O's now but it was something easy yet important for us as far as i remember.
Originally posted by yiha093:er. if i not wrong.
syallbus only until 4 nia. the carbon required in syallbus. 5072?
ok maybe what i saying is beside the point. sorry.
4C is damn pathetic if that is all you all learn these days.Theres little variation u can make with 4C and you will hardly learn much or anything useful since 4C won't make u understand the importance of the longest chain.
We used to learn till 10C. tr@nsp0rt_F3V3R told me they all study till 6C so thats the limit i set my questions to though 6C is rather limited and no fun to play with :p
Originally posted by dkcx:4C is damn pathetic if that is all you all learn these days.Theres little variation u can make with 4C and you will hardly learn much or anything useful since 4C won't make u understand the importance of the longest chain.
We used to learn till 10C. tr@nsp0rt_F3V3R told me they all study till 6C so thats the limit i set my questions to though 6C is rather limited and no fun to play with :p
my cher is new de. so everything he follow what we have to learn. ._.
but he does teach us how to name. yea. lol X.X
Originally posted by yiha093:my cher is new de. so everything he follow what we have to learn. ._.
but he does teach us how to name. yea. lol X.X
It won't hurt knowing more especially if u intend to do H1 or H2 chem in JC or just for some knowledge since the O's syllabus portion on organic chemistry has always done it injustice and is rather pathetically shallow.
Considering that the bulk of the chemistry researches are mainly organic synthetic chemist, O's prefers to add in some rather redundent material rather than focusing on some of the more useful materials that can be taught.
ya but if a particular student already cant do up to 6 C for O lvl whats the point of going there when only req is 4C ? besides... you know how to name can apply for most of the Carbon le what. its just the term that one needs to know ?
sorry if i seem prudent O.O
Originally posted by yiha093:ya but if a particular student already cant do up to 6 C for O lvl whats the point of going there when only req is 4C ? besides... you know how to name can apply for most of the Carbon le what. its just the term that one needs to know ?
sorry if i seem prudent O.O
4C is seriously rather worthless if organic chem naming is supposed to be taught since the only thing can that come out from a 4C molecule is a methylbutane or if i wan a 2,3-dimethylbutane.
Base on anpanman understanding, yes he might get the answers if asked in exams correct PURELY because butane can only have a methyl and not ethyl etc. When i move on to 6C and test on ethyl, non linear chains etc, its very clear that the entire understanding and concept of naming organic molecules is entirely wrong. That is what i want to correct.
If you understand how to do proper naming, 6C 10C there is simply no difference. Understanding 4C and think u understand what is naming of organic molecules and that is seriously wrong due to the limitations and variations 4C can provide.
Its important to understand the concept rather than continuously having the wrong concept throughout ur O's and just get your answers correct purely because of the limitations of the questions. Answers are never important but the process of thinking is.
U intend to go JC as far as i remember and if u do intend to do H1/H2 chem, u BETTER understand the concept of organic naming since it would be difficult for u to change and learn the proper naming if u have been using a totally wrong concept throughout your O's.
Besides anpanman, i haven't seen any input in trying the questions from u yiha093 nor any of the other O's takers. If u understand the concept, the easier 3 questions should totally be a piece of cake and if you are unable to provide me with the correct answer or your answers are similar to what anpanman has provided, maybe you should consider learning what is right and not just tell yourself that all you need know is 4C.
Originally posted by dkcx:If the above is too hard, try these 1st which are much easier. I'll explain these and the above later tonight when i back if u can't figure them out and noone else explains to u.
a) C - C - C - C - C
|
C
b) C - C - C - C
| |
C C
c) C - C - C
| | |
C C C
Understood your lastest explanation
So here's the answer for (b) and (c)
C - C - C - C
| |
C C
b . methyl pentane (I highlighted the longest C chain)
c.
C - C - C
| | |
C C C
Still not very sure of this. But the way I look at it, the longest C chain is as highlighted.. Err still methyl pentane? high chances of getting it wrong.
And regarding getting the O's organic chem questions, i don't mind settling just for any basic questions. Just eager to get my hands on questions to try out to test my understanding. thanks
Originally posted by anpanman:
Understood your lastest explanationSo here's the answer for (b) and (c)
C - C - C - C
| |C C
b . methyl pentane (I highlighted the longest C chain)
c.
C - C - C
| | |
C C CStill not very sure of this. But the way I look at it, the longest C chain is as highlighted.. Err still methyl pentane? high chances of getting it wrong.
Yes a) b) c) are all the same compound and all are 3-methylpentane.
The reason for giving these 3 questions is i want you and anyone who bothers to read and try to know that the same compound can be drawn differently yet is the exactly the same thing.
I do hope you understand why i have to add the 3 in front and do note that for anything above 3C, you will need the numbering to be officially correct.
Feel ready to attempt the more difficult 3 now? They should be something out of the O's syllabus but will be needed for A's or poly chemistry. If u are interested to learn and try, just read on if not you can stop where you are.
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C - C - C - C - C - C - C - C
| |
C C
With the main chain highlighted, this organic compound has a straight chain of 8C making it an octane. It also has 2 methyl groups (not ethyl). If you call this methyloctane, this just means there is 1 methyl group so how we name this will be calling it dimethyloctane.
For organic chemistry, we can name things using mono (1), bi (2), tri (3), tetra (4) etc if there is more than 1 of the same thing such as diethyl, trimethyl etc to a compound to tell the person the number of such groups in a molecule.
The proper name for the above molecule will be 3,5-dimethyloctance (NOT 4,6-dimethyloctane)
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C - C - C - C - C - C - C - C
| |
C C - C
Now in this compound, we have the same octane parent chain and a methyl and an ethyl group. For naming of such a molecule, you will need to mention both side chains so this molecule is called 5-ethyl-3-methyloctane.
The 5 and 3 are to tell people the location of such side chains and whether it is a methyl, ethyl, propyl etc.
For naming of side chains, it will be done by alphabetical order so E comes before M so ethyl comes before methyl even though methyl is a smaller chain and it comes earlier at position 3.